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United States Department of Agriculture

Agricultural Research Service

Research Project: Evaluation, Enhancement, Genetics and Breeding of Lettuce, Spinach, and Melon

Location: Crop Improvement and Protection Research

Title: Histological Aspects of Cucumis melo PI 313970 Resistance to Podosphaera xanthii and Golovinomyces cichoracearum

Authors
item Sedlarova, Michaela - PALACKY UNIVERSITY
item Lebeda, Ales - PALACKY UNIVERSITY
item Miksikova, Pavla - PALACKY UNIVERSITY
item Duchoslav, Martin - PALACKY UNIVERSITY
item Sedlakova, Bozena - PALACKY UNIVERSITY
item McCreight, James

Submitted to: Journal of Plant Diseases and Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 29, 2009
Publication Date: August 1, 2009
Citation: Sedlarova, M., Lebeda, A., Miksikova, P., Duchoslav, M., Sedlakova, B., Mccreight, J.D. 2009. Histological Aspects of Cucumis melo PI 313970 Resistance to Podosphaera xanthii and Golovinomyces cichoracearum. Journal of Plant Diseases and Protection 116: 169-176.

Interpretive Summary: Fruit yield and quality of muskmelon, a.k.a. cantaloupe, can be reduced by powdery mildew caused in the U.S. by the fungus Podosphaera xanthii. Many physiological or pathogenic races of powdery mildew are known in the U.S. and worldwide, and many sources of host plant resistance provide effective resistance against most of the races. Two other fungal species are also known to cause powdery mildew in Europe. The USDA-ARS melon project in Salinas reported resistance in PI 313970 to several races of powdery mildew incited by Podosphaera xanthii and also noted a unique response to powdery mildew characterized by resistant blisters that appear long after leaves and stems of susceptible melon varieties are heavily infected by the disease. This research looked at the interactions of two powdery mildew fungi (Podosphaera xanthii and Golovinomyces cichoracearum) from Czech Republic on PI 313970. At least two different resistance mechanisms were found operating in PI 313970. The first mechanism delays pathogen development. The second mechanism results in reduced pathogen reproduction. This second mechanism may be found to produce the resistant blister symptom with its accompanying features of water soaked tissues and higher incidence of hypersensitive-like, necrotic cells. It must be noted that development of resistant blisters on PI 313970 have yet to be demonstrated in response to infection by G. cichoracearum. Further research may, thus, demonstrate that resistant blisters, which are very unusual in plant-powdery mildew interactions, result from a third and unique mechanism of resistance to infection by P. xanthii. The potential role and usefulness of the resistant blister reaction in reducing quality and yield losses to powdery mildew of melon remain are unknown.

Technical Abstract: Cucumis melo accession PI 313970 possesses numerous genes for race-specific resistance to powdery mildew incited by Podosphaera xanthi, but it also exhibits non-race-specific, resistant blister leaf reactions in California, U.S.A. to several races of P. xanthii. Light microscopic examination confirmed the presence of mycelia, conidiophores and conidia, and limited numbers of necrotic cells in the water-soaked blisters. Interactions of PI 313970 with Czech isolates of cucurbit powdery mildew incited by P. xanthii and Golovinomyces cichoracearum, were followed in a comparative study with susceptible cucumber (Cucumis sativus L.) 'Stela' on leaf discs through 144 h post inoculation (hpi). Spore production, germ tube development and infection rate of both pathogens were reduced on PI 313970 which expressed delayed resistance responses including limited hypersensitive response (HR) to these two powdery mildew pathogens. At least two different resistance mechanisms are operating in PI 313970. The first mechanism delays pathogen development (conidial germination and appressoria formation). The second mechanism is probably based on specific physiological and biochemical processes leading to reduced pathogen reproduction with minimal or no HR. This second mechanism may, under different parameters (intact leaves, longer time period, pathogen isolate to which PI 313970 expresses race-specific resistance, etc.), be found to produce the resistant blister symptom with its accompanying features of water soaked tissues and higher incidence of HR-like, necrotic cells. It must be noted that development of resistant blisters on PI 313970 have yet to be demonstrated in response to infection by G. cichoracearum. Further research may, thus, demonstrate that resistant blisters, which are very unusual in plant-powdery mildew interactions, result from a third and unique mechanism of resistance to infection by P. xanthii.

Last Modified: 8/21/2014
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